Physical activity and risk of stroke in women

Context Persuasive evidence has demonstrated that increased physical activi ty is associated with substantial reduction in risk of coronary heart disea se. However, the role of physical activity in the prevention of stroke is l ess well established. Objective To examine the association between physical activity and risk of total stroke and stroke subtypes in women. Design and Setting The Nurses' Health Study, a prospective cohort study of subjects residing in 11 US states. Subjects A total of 72 488 female nurses aged 40 to 65 years who did not ha ve diagnosed cardiovascular disease or cancer at baseline in 1986 and who c ompleted detailed physical activity questionnaires in 1986, 1988, and 1992. Main Outcome Measure Incident stroke occurring between baseline and June 1, 1994, compared among quintiles of physical activity level as measured by m etabolic equivalent tasks (METs) in hours per week. Results During 8 years (560087 person-years) of follow-up, we documented 40 7 incident cases of stroke (258 ischemic strokes, 67 subarachnoid hemorrhag es, 42 intracerebral hemorrhages, and 40 strokes of unknown type). In multi variate analyses controlling for age, body mass index, history of hypertens ion, and other covariates, increasing physical activity was strongly invers ely associated with risk of total stroke. Relative risks (RRs) in the lowes t to highest MET quintiles were 1.00, 0.98, 0.82, 0.74, and 0.66 (P for tre nd = .005). The inverse gradient was seen primarily for ischemic stroke (RR s across increasing MET quintiles, 1.00, 0.87, 0.83, 0.76, and 0.52; P for trend = .003). Physical activity was not significantly associated with suba rachnoid hemorrhage or intracerebral hemorrhage. After multivariate adjustm ent, walking was associated with reduced risk of total stroke (RRs across i ncreasing walking MET quintiles, 1.00, 0.76, 0.78, 0.70, and 0.66; P for tr end = .01) and ischemic stroke (RRs across increasing walking MET quintiles , 1.00, 0.77, 0.75, 0.69, and 0.60; P for trend = .02). Brisk or striding w alking pace was associated with lower risk of total and ischemic stroke com pared with average or casual pace. Conclusion These data indicate that physical activity, including moderate-i ntensity exercise such as walking, is associated with substantial reduction in risk of total and ischemic stroke in a dose-response manner.